Electric-wave-translation system



April 23, 1929. E, B E 1,710,254

ELECTRIC WAVE TRANSLATION SYSTEM Filed Aug. 8, 1925 //7 var? far. [ammd Brace Patented Apr. 23, 1929 units!) STATES PATENT OFFICE.

EDliil D BRUCE, 6F RED BANK, NEW JERSEY, ASSIGNOR TO W ZSTERN ELEOTRLC CGIYI PANY, INCORPORATED, llEVJ YORK, H. Y., A CORPORATION 0.1 I l l'il'W YGRX.

LELECTRIC-WAVE-TRANSLATION SYEETEM.

Application on August 8, 1925. sci-mine. 43,938.

This invention relates to electric Wave translation systems, and more particularly to improved coupling arraugenients "for coupling .local oscillators to heterodyne radio receiving systems.

ln radio receiving systems wherein a local oscillator is: employed to supply combining oscillatitms for reducin the in piencyol the incoming wave to a desired lower l reqiumcy level it is very desirable to prevei'it the radiation from the receiving anterma of waves generated by the oscillator. This is tobe desired, because of the lll-CQllllOOL of causing serious interferencewvith i'iearby receiving sets.

li hen using a radio receiver of the type referred to above and including a local oscillator directly coupled to the antenna circuit, i; is also often desirable to be able to adjust the tuuin oi the antez'ina, such as a loop antenna, v'ithout varyingthe amount of enere'y supplied by the local oscillator to the detector. A specific instance \vhereitis linportant to be able to accomplish this is in receiving systems employed for field strength ineainireiucnts, if the re'eiving' circuit is such that the oscillator voltage varies with rluu'iges in tuning; oi the antenna, the circuit will be or" little use 'lor field strength measurements because erroneous readings are likely to he obtained. This results ti'roin the ilt'll lllitll the intermediate frequency voltage a a luucrodyne circuit is substantially proportional to the product of the voltage. oi receivcd waves and the voltage of the locally )lied waves. It is tl wrelore, clear that i the voltage of local Waves is varied by the "uniug of the receiving circuit, the Il'lZlXlllll'lll'l voltage oi. the intermediate trequency Waves may occur when the receiving circuit is tuned, to a frequency other than the frequency oi? received \vaves. This will be evident from the fact that when the tuning oi. a receiving circuit is varied, the change in its adn1iittance for received Waves may be dillerent from its change of admittance for locally supplied Waves.

It is an object of this iuventionto prevent waves from being radiated from a receiving antenna.

Another object is to prevent changes in tuning of a receiving circuit from affecting the voltage of Waves supplied by a local oscillater to a space discharge repeater associated with the receiving circuit;

Another object is to transmit signal waves and local oscillations to a space discharge device. over an adjustable resonant path Without changing the value of its admittance for local oscillations when the tuning of the resonant path is varied.

An additional object is to prevent erroneous indications of the voltage oil received Waves.

A feature of the invention is a balancci'l coupling arraiug'einent of an antenna, oscillator and detector.

A l'urther f ature is a balanced coupling device so associateo with an oscillation gencrater, a detector, and a receiving circuit that the tuning of the receiving circuit will have no effect upon the voltage of local oscillations supplied to the detector.

A rurther feature is a transformer having windings included in a closed receiving circuit and another winding coupled thereto and included in a local oscillator circuit.

A still further feature is a space discharge tube detector including a path lier. balancing the inherent reactive path through the tube and having a receiving circuit and an oscillator associated with. the tube in such manner as not to disturb the balance of the circuit, whereby the tuning, of the receiving circuit only be varied Without ulleotinp; the

voltage of Waves supplied by the oscillator to the detector.

for transmitting a plurality of different waves from separate sources to a common receiving device. Certain elements of the system are adapted toperuiit waves from one of the sources to traverse the variable.

H W .xm s-- p-i- .1. .1 par \vlt iout raving c an v0 cage manger as a result of variations in the zulniittance of the path.

For practical use, the invention may be embodied in a radio receiving system or? the type employing local oscillators for receivinc; by the hcterodyne method. able path may be a resonant receiving ci1- cuit, including forexaniple, a loopantenna and certain windings of a balanced transformer. Otheru'indings of this transformer The va rioscillations through the in st ch manner that their vol 7 be tuned to the frequency of received I tector 30,

may be included in appropriate circuits of a space discharge tube for the generation of oscillations as Well as for transmitting these iying circuit to a ,other space discharge tube, which may e a detector.

Signal'i ayes impressed upon the receiving ci cuit may be combined Withlocal oscillations in the oetector to produce an intermediate frequency Wave. Theyoltagc of the intermediate Waves may 1GPS3HL the Voltage of receiredwayer, since i 'eratcd \RUGS are supplied ed by z djustinents made in the receiving circuit. This circuit In Fig. 1 of the drawings, the 1' is illustrated in connection with dyne radio receiving system.

In Fig. a modification of the circuit 0t Fig. 1 to the leftof the dotted line is illustrated.

The 'a-dio receiving circuit shown in Fig. 1 of the d swing includes an antenna 10, in this ins a ice illustrated as a loop antenna; a. heterodyne oscillator 20, balanced coupling transformer 13, a high trequency dean intermediate frequency ainplitier 4G, a low frequency detect r and alow frequei cy anipliiier 51. he loop antenna 10 has its outer terminals connected to an adjustable tuning condenser 11. @no outer terminal is connected to the control electrode o't' syncs discharge tube 31. The other outer terminal. is connected to the ground through the condenser 32 which is adapted to balance the etlectiye input capacity of the discharge device 31, whereby the high ircwp ency receiving circuit is rendered symmetrical Witu' respect to the oscila. heterolater 20.

at e

rate .y in the input and output circuits oi? the space discharge tube oscillator 21. These windings have one terminal of sch connected to the control electrode and anode respectively of tube 21. The input circuit 7 traceable from its control electrode through winding 1% to ground thence to the cathode ot tube 21, via the cathode of tube 52. A suitable polarizingpotential is supplied to the control electrode of the tube. 21 by the drop in potential alo the filament of tube 1%- and 15 of trans- I of tube 21 T dis-cueings of transfori The ice discharge tube 31 has an output circuit connected to its anode including the 1' of transformer 33 (shunted ance Bl) arranged in series "no space. er it battery 5. the oppoof which is connected to the The output circuit of ed'to the innut circuit of inter- L amplifier 10 by transformer includes the two space iii uei i r c cs -21 and 12. The output circuit of tube iscoupled'to the input circuit or" a second detector 50,including the space u scha '3)" tube having asuitable blocking condenser ar rid leak resistance 55 inl i i t. The output circuit of i r oupied to an audible frecu ncy an'zoiifier to 3e 53 ha iig suitable output terminals 6 an; 5. for c n iection to any desired tlQVPC such as telephone receivers, ioudspcalnng receiver, a wire line or the lilie.

Condensers 35 9.116 36 are provided to suply oi" lil'lltrttilCo pa 'hs for high frequency N2"" around the space cu rent source 5d in l around the filaments ot tubes 52 21, 53, 42 and 11 in the other.

e secondary Jindings 12 of the coupling transformer 13 may be constructed by meretwisting together a short length of the loop conductors at the points who 'e the windings 12 are shown coiniected they may be ordinary soienoidiu windings ar 'anged to be inducti 'ei r coupled. The primary windings 1 1 and 1' niay be suitably positioned with g 12, F or e nple they arranged 'coa.\ial with the lg the oscillator 20"(0 the loop 0, which may also be an ordinary ice to which, it desired, an open ancoupled, "he point inc icated, 1 bridge arrangement results, the balance oi? which is independent of frequency. lhe current inducer in windings 12- divides een the two halves of the loop a or inductance 10 so'that no difierpotential is produced at the. terminals 2% and hence, the magnitude of the In ordertolurther prevent an unbalance in the circuit, by virtue of any direct supply of waves from the oscillator to the antenna 10 by radiation, the oscillator isshielded from the antenna and also from the tuning comlenser. The latter is included in a separate shieldin compartment. The restof the receiving circuit is also included in a separate shielding con'ipartment. The shield represented by the lM'OhZQIl line 25.

\Vhen the circuit is in operation, radio waws of any sort may be received by antenna 10 and will. establish a voltage therein. One hall of this voltage is applied to tube 31 between itscontrol electrode and cathode, be-

cause these electrodes are coi'inected between the mid-point and one terminal'ol the loop. lVaves from oscillator 20, which preferably have a frequency ditl cring from that 01" the received wave, are also supplied to the input circuit of tube 31 and are con' bined with the received waves to produce intermediate lirequency waves or in'alulible but readily amplitiable frequency. 'The voltage of the intermediate frequency waves is substantially noportional to the product oil: the voltages oi received and locally supplied waves.

The intermediate frequency waves'are detected in the second detector 50 and the detected current-is amplified in the circuit including tube 53. At the terminals 56 and 57, low frequency waves are available and the voltage of these waves is proportional to the voltage. or intensity of the waves rc ceived by antenna 10, because the voltage of local waves from oscillator are constant and unaffected by the tuning of the loop.

In the. coupling arrangement of the in vention undesired capacity to qround effects of the windings 12 of transformer 13 are avoided by the ground connection at the common terminal. By this connection also the loop circuit is stabilized as regards its capacity to ground.

Another advantage of the arrangementdescribed is that the couplii'ig transformer is :nibstantially non-imluctive in relation to the antenna and hence has no effect upon the resonance point of the receiving circuit.

By coupling the oscillator to the control electrode circuit instead of the plate circuit of tube 31, advantage istaken of the amplitying power of the tube and radiation oi:

locally generated waves is prevented by the fact that these waves divide equally between the two halves of the loop antenna. N 0 in terference with other receiving circuits will therefore be produced.

In F 2, a modification of the portion of the circuit to the left of the dotted line n w on Fig. 1 is shown. This figure includes the antenna 10 with its tuning condenser 11, balancedtransformer 14, oscillator 20 including the tube 21. and a portion of the amplifier tube 31. This circuit differs from the corresponding portion of the circuit of Fig. 1 intha-t the right-hand secondary winding of transformer let not connected directly to ground, but by. a path including" the condenser in series with theoscillation generator til. The condenser and the generator (it are shunted by an adjustable re sistance circuits are identical.

The arrangement shown in a local. oscillator (ll to supply Fig. 2 enables waves i'jor com 'parison or for calibration purposes and is adapted to permit the'oscillator (31 to be connccted to the circuit without causii'ig unbalance thereof. This is accoinplisl ed by connecting the oscillator (3l to points corresponding to the points of connection of the tcruiinals of the antenna 10. Waves are sup plied by oscillator 61, at a time when no waves are being received by the antenna. The waves from oscillator (31 a re combined with waves from the oscillat 21. in the same manna as waves received on the antenna. were combinod therewith.

'lhe adjustable resistance (Bis provided to permit the amplitude of the oscillations supplied by the source 61 to be adjusted to a de sired value, For example, the amplitude of an incoming signal wave may be measured by utilizing the source 61 to sinnilate the re: ceived wave. This is accomplished by supplying oscillations from the source 61 and adjusting the an'ipliinde oi the oscillations to such value that the output voltage at ter urinals 50 and 57 is the same for oscillations from source (ll as for received waves. The an'iplitude oi the oscillations supplied by source 61 being known, the amplitude of the received waves may .be readily determined.

Switch 63 is provided to permit the winding 12 to be connected to gronnd t'or ordi nary reception, or to the oscillator (ll for measurement or calibration jun-poses. It is to, he noted. that the auxiliary source 61 is coimccted, to the terminal of the winding 12 which is normally grounded, whereby the balance of the receiving circuit is Innlisturbed when the source 61 conuec :ed to the systen'i.

F or ordinary reception purposes the transformer 13 need only be in'ovidetl with a single secondary winding; 12 in place of the two windings illustrated in Fig. 1.

The arrangement is only ilh'istrativc of one embodiment of the many in which the i n vention may be incorporated. For example, the position of the coupling transformer may i be modified without changing the principle of operation and other changes and embodiments will, of course, readily suggest themselves to persons skilled. in the art, without the exercise of any inventive effort. The limits ol. the invention are therefore defined only by the scope of the appended. claims.

What is claimed is: c y

1. In combination, an inductance, a transln all other respects the two nected to said antenna, a balanced trans former connected between said antenna and ground, and an oscillation generator symmetrically connected to saidantenna to transmit waves through said antenna to said repeater, whereby the voltage of said waves is independent of changes in tuning of said antenna. j

. 3. In combination, an inductance, variable condenser connected to outer terminals of said inductance, a space discharge repeater having electrodes also connected to said outer terminals, a transformer having two equal windings connected in series with said inductance at its electrical center, said windings having a common terminal connected to ground, other windings for said transformer, an oscillation generator including input and output circuits, said other windings being connected in said input and output circuits, said oscillator being in. conjugate relation with respect to the path through said variable condenser.

1. In combination, an antenna, an oscillation generator, a space discharge repeater coupled to said antenna, means for transmitting waves from said generator to said repeater, said'means including said antenna and a transiormer having windings in balanced relation thereto, said means being adapted'to prevent radiation waves from said antenna.

5. In combination, a loop antenna having terminals, a space discharge tube including a cathode, anode and'control electrode, a connection from one terminal of said antenna to said control electrode, a connection from another terminal or" said antenna to ground through condenser, a variable condenser connected across the terminals of said antenna, an oscillation generator, and means for coupling said generator to said loop in such manner as t c produce no difierence of potential at said terminals, said means com prising a transformer having windings included in said antenna circuit at its electrical mid-point.

6. In a radio receiving system, a loop antenna, a variable condenser connected to terminals of st 1d loop, a space discharge rcpeater having electrodes connected in balanced relation to said loop and means tor compens; sing the etlective input capacity of said repeater, an oscillation generator, and means for coupling said generator'to said repeater whereby the voltage of said oscillator is ii dependent of said repeater circuit w hout all'ecting said balanced connection, said means including a four or mcr having two secondary windings with common terminal connected to ground.

7. In a radio receiving system, a space dischage oscillator and a space discharge rea balanced transformer having two s connected to said oscillator and two connected to said repeater, said windings pairs oi windings forming elements of separate resonant circuits for said repeater and oscillator, and means whereby the tuning of said resonant circuit may be adjusted for said repeater without aliecting the voltage of waves from said oscillator.

S. In a radio receiving system, a tuned oscillating circuit, an antenna circuit comprising a tuned loop, a transformer having winding '11 eachoi? said circuits, a space cistharge rep-eater having a cathode, an anode and a grid control electrode,a connection from one terminal of said loop to the grid controlelectrode, a connection from the other terminal ot said loop to the cathode of said repeater, said last mentioned connection including a condenser for balancing the grid to cathode capacity of said repeater, and a connection i romthe mid-point of said antenna to ground- 9. In a heterodyne receiving system, a loop antenna, a repeater having an input circuit, an oscillator, means for coupling said oscilazor to said antenna and to said input circuit, said antenna having a connection to ground mid-point and connections to ground including equal capacities from the terminals of said antenna.

In witness whereof, I hereunto subscribe my name this third day of August, A. D.

EDMOND BRUCE.

winding trans- Lil 

